U.S. patent application number 12/948094 was filed with the patent office on 2012-05-17 for apparatus and methods for delivering a heated fluid.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Andrew W. Chen, Andrew R. Fox, Scott A. Jerde, William P. Klinzing, Bradley K. Kucera, Patrick J. Sager.
Application Number | 20120121238 12/948094 |
Document ID | / |
Family ID | 46047832 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120121238 |
Kind Code |
A1 |
Chen; Andrew W. ; et
al. |
May 17, 2012 |
APPARATUS AND METHODS FOR DELIVERING A HEATED FLUID
Abstract
Herein are disclosed apparatus and methods for delivering a
heated fluid. The apparatus comprises at least a preheat zone, an
expansion zone, and an expanded zone comprising a plurality of trim
heaters, at least one fluid flow-distribution sheet, and an
outlet.
Inventors: |
Chen; Andrew W.; (Woodbury,
MN) ; Fox; Andrew R.; (Oakdale, MN) ; Jerde;
Scott A.; (Maplewood, MN) ; Klinzing; William P.;
(West Lakeland, MN) ; Kucera; Bradley K.;
(Lakeville, MN) ; Sager; Patrick J.; (Hastings,
MN) |
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
46047832 |
Appl. No.: |
12/948094 |
Filed: |
November 17, 2010 |
Current U.S.
Class: |
392/465 |
Current CPC
Class: |
D04H 1/54 20130101; F24H
9/2028 20130101; D04H 3/08 20130101; D04H 3/16 20130101; F26B
13/108 20130101; D04H 3/14 20130101; F24H 1/102 20130101; F24H
9/0021 20130101; F24H 9/128 20130101; D06C 7/00 20130101 |
Class at
Publication: |
392/465 |
International
Class: |
B67D 7/80 20100101
B67D007/80 |
Claims
1. An apparatus for handling, heating and delivering a fluid,
comprising: a preheat zone comprising a preheater; an expansion
zone fluidly connected to the preheat zone; an expanded zone
fluidly connected to the expansion zone and comprising a downstream
axis and a lateral extent and a tertiary extent, the expanded zone
further comprising: a plurality of trim heaters collectively
extending across at least a portion of the lateral extent of the
expanded zone, at least one fluid flow-distribution sheet, and, an
outlet.
2. The apparatus of claim 1 wherein the plurality of trim heaters
collectively extend across the lateral extent of the expanded
zone.
3. The apparatus of claim 1 wherein the trim heaters comprise
electrical resistance heaters.
4. The apparatus of claim 3 wherein the preheater comprises a heat
exchanger configured to heat the fluid by exchanging thermal energy
to the fluid from a preheating fluid.
5. The apparatus of claim 1 wherein the at least one fluid
flow-distribution sheet is positioned downstream of the plurality
of trim heaters.
6. The apparatus of claim 1 wherein the fluid flow-distribution
sheet comprises a perforated sheet with the perforations providing
a percent open area of from about 30% to about 70% and having an
average size of from about 0.06 inch (1.5 mm) to about 0.40 inch
(10 mm).
7. The apparatus of claim 1 comprising at least two fluid
flow-distribution sheets arranged in series along the downstream
axis of the expanded zone.
8. The apparatus of claim 1 comprising at least three fluid
flow-distribution sheets arranged in series along the downstream
axis of the expanded zone.
9. The apparatus of claim 8 wherein the at least three fluid
flow-distribution sheets are spaced apart along the downstream axis
of the expanded zone by distances equal to or greater than the
tertiary extent of the expanded zone.
10. The apparatus of claim 1 wherein the outlet is spaced
downstream from the fluid flow-distribution sheet that is closest
to the outlet, by a distance that is greater than the tertiary
extent of the expanded zone.
11. The apparatus of claim 1 wherein the outlet comprises a working
face and wherein the expanded zone comprises a plurality of
temperature sensors spaced across the lateral extent of the
expanded zone and positioned a distance upstream from the working
face of the outlet that is greater than about 30% of the tertiary
extent of the expanded zone, with a temperature-sensitive tip of
each temperature sensor protruding into the fluid.
12. The apparatus of claim 1 wherein the expansion zone comprises a
lateral expansion factor of at least 3.5 and a tertiary contraction
factor of at least 4.0.
13. The apparatus of claim 1 wherein the expansion zone comprises a
lateral expansion factor of at least 5.0 and a tertiary contraction
factor of at least 5.0.
14. The apparatus of claim 1 wherein the expansion zone comprises a
lateral expansion angle of at least 15 degrees.
15. The apparatus of claim 1 wherein at least the expanded zone
comprises thermal insulation that surrounds at least a portion of
the expanded zone.
16. The apparatus of claim 1 wherein the outlet comprises a working
face with an aspect ratio of at least 35:1.
17. The apparatus of claim 1 wherein the apparatus further
comprises a fluid-suction apparatus configured to be placed on the
on the opposite side of a fluid-permeable, moving substrate from
the outlet, wherein the fluid-suction apparatus has a lateral width
at least as wide as the lateral width of the substrate.
18. The apparatus of claim 1 wherein the expanded zone comprises a
laterally-oriented hinge.
19. A method of passing a heated fluid through a moving,
fluid-permeable substrate, comprising: preheating a fluid; passing
the preheated fluid through an expansion zone; passing the
preheated fluid through an expanded zone, exposing at least a
portion of the preheated fluid to at least one of a plurality of
trim heaters within the expanded zone, passing at least a portion
of the preheated fluid through at least one fluid flow-distribution
sheet within the expanded zone; and, passing the preheated fluid
through an outlet of the expanded zone onto the moving,
fluid-permeable substrate and passing it through the substrate;
and, capturing and removing at least a portion of the fluid passed
through the substrate, by a fluid-suction apparatus located on the
opposite side of the substrate from the outlet.
20. The method of claim 19 wherein the moving, fluid-permeable
substrate is a monocomponent melt-spun fibrous mat comprising
monocomponent organic polymeric fibers.
21. The method of claim 19 wherein the expanded zone comprises a
plurality of temperature sensors downstream from the trim heaters,
and wherein the fluid temperature readings monitored by the
temperature sensors are used to control the power supplied to the
trim heaters.
22. The method of claim 21 wherein the trim heaters collectively
extend across a lateral extent of the expanded zone, wherein the
temperature sensors are spaced across the lateral extent of the
expanded zone, and wherein the power supplied to each trim heater
is controlled based on the fluid temperature reported by a
temperature sensor that is generally downstream of, and laterally
aligned with, that trim heater.
23. The method of claim 19 wherein the trim heaters additionally
heat the preheated fluid by a temperature increment of less than
about 3 degrees C.
Description
BACKGROUND
[0001] Heated fluids are often delivered to substrates, e.g. moving
web-like substrates, for a variety of purposes. For example, heated
fluids may be impinged upon a substrate for purposes of bonding,
annealing, drying, promoting a chemical reaction, and the like.
SUMMARY
[0002] Herein are disclosed apparatus and methods for delivering a
heated fluid. The apparatus comprises at least a preheat zone, an
expansion zone, and an expanded zone comprising a plurality of trim
heaters, at least one fluid flow-distribution sheet, and an
outlet.
[0003] Thus in one aspect, herein is disclosed an apparatus for
handling, heating and delivering a fluid, comprising: a preheat
zone comprising a preheater; an expansion zone fluidly connected to
the preheat zone; an expanded zone fluidly connected to the
expansion zone and comprising a downstream axis and a lateral
extent and a tertiary extent, the expanded zone further comprising:
a plurality of trim heaters collectively extending across at least
a portion of the lateral extent of the expanded zone, at least one
fluid flow-distribution sheet, and, an outlet.
[0004] Thus in another aspect, herein is disclosed a method of
passing a heated fluid through a moving, fluid-permeable substrate,
comprising: preheating a fluid; passing the preheated fluid through
an expansion zone; passing the preheated fluid through an expanded
zone, exposing at least a portion of the preheated fluid to at
least one of a plurality of trim heaters within the expanded zone,
passing at least a portion of the preheated fluid through at least
one fluid flow-distribution sheet within the expanded zone; and,
passing the preheated fluid through an outlet of the expanded zone
onto the moving, fluid-permeable substrate and passing it through
the substrate; and, capturing and removing at least a portion of
the fluid passed through the substrate, by a fluid-suction
apparatus located on the opposite side of the substrate from the
outlet.
[0005] These and other aspects of the invention will be apparent
from the detailed description below. In no event, however, should
the above summaries be construed as limitations on the claimed
subject matter, which subject matter is defined solely by the
attached claims, as may be amended during prosecution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a front-side perspective view of an exemplary
apparatus as disclosed herein.
[0007] FIG. 2 is a side view of the exemplary apparatus of FIG.
1.
[0008] FIG. 3 is a front view of a portion of the exemplary
apparatus of FIG. 1.
[0009] FIG. 4 is a side cross sectional view of a portion of the
exemplary apparatus of FIG. 1, taken along the line marked 4-4 in
FIG. 1.
[0010] FIG. 5 is a front cross sectional view of a portion of the
exemplary apparatus of FIG. 1, taken along the line marked 5-5 in
FIG. 1.
[0011] FIG. 6 is a side perspective view of an exemplary apparatus
as disclosed herein, further comprising a fluid-suction
apparatus.
[0012] Like reference numbers in the various figures indicate like
elements. Some elements may be present in identical or equivalent
multiples; in such cases only one or more representative elements
may be designated by a reference number but it will be understood
that such reference numbers apply to all such identical elements.
Unless otherwise indicated, all figures and drawings in this
document are not to scale and are chosen for the purpose of
illustrating different embodiments of the invention. In particular
the dimensions of the various components are depicted in
illustrative terms only, and no relationship between the dimensions
of the various components should be inferred from the drawings,
unless so indicated. Although terms such as "top", bottom",
"upper", lower", "under", "over", "front", "back", "outward",
"inward", "up" and "down", and "first" and "second" may be used in
this disclosure, it should be understood that those terms are used
in their relative sense only unless otherwise noted.
DETAILED DESCRIPTION
[0013] Shown in FIG. 1 in side perspective view, and in FIG. 2 in
side view, is an exemplary apparatus 1 which may be used to deliver
a heated fluid. Apparatus 1 is a fluid heating and handling
apparatus that comprises several zones (units) that are defined at
least by major walls and that are fluidly connected to each other
as disclosed herein. The various zones of apparatus 1 will be
described herein with respect to the downstream, lateral, and
tertiary axis of each zone. For each zone, the downstream axis "d"
is the axis generally aligned with the overall flow of fluid
through that zone, as shown in FIG. 1. The downstream direction is
the direction of overall fluid flow along this axis; the upstream
direction is the opposite direction along the same axis. At any
point in a zone, the lateral axis "l" is the longest axis that is
orthogonal to downstream axis "d" of that zone. For example, the
lateral extent of expansion zone 20 at any particular point along
the downstream axis "d" of expansion zone 20 will be the distance
between minor walls 23 and 24 along a line passing through that
point of the downstream axis. Similarly, the lateral extent of
expanded zone 30 at any particular point along the downstream axis
of expanded zone 30 will be the distance between minor walls 33 and
34 along a line passing through that point of the downstream axis
of expanded zone 30.
[0014] For each zone, the tertiary axis "t" is the shortest axis
that is orthogonal to downstream axis "d" of that zone (and will
also be orthogonal to lateral axis "l" of that zone). For example,
the tertiary extent of expansion zone 20 at any particular point
along the downstream axis of expansion zone 20 will be the distance
between major walls 21 and 22 along a line passing through that
point of the downstream axis. Similarly, the tertiary extent of
expanded zone 30 at any particular point along the downstream axis
of expanded zone 30 will be the distance between major walls 31 and
32 along a line passing through that point of the downstream axis
of expanded zone 30. The terms tertiary axis and tertiary extent
are used herein for convenience in distinguishing them from the
lateral axis or extent, and does not signify or require that the
tertiary axis of a particular zone of apparatus 1 is necessarily
aligned with the Earth's gravity. And, as is evident from FIG. 1,
the downstream, lateral and/or tertiary axis of a particular zone
of apparatus 1 may not be aligned with that of another zone of
apparatus 1.
[0015] Apparatus 1 comprises a preheat zone 10 which comprises an
inlet configured to receive a stream of fluid (e.g., air, as
motivated by a blower) and which comprises one or more preheaters
11 (shown in idealized representation in FIGS. 1-3). Preheat zone
10 is shown in FIG. 1 as generally rectangular in cross section,
but may be oval, circular, and so on. (In the particular case of a
circular cross section, there may be no distinction between the
lateral and tertiary axes of preheat zone 10). Preheater 11 may
comprise any suitable heat source that may heat the fluid passing
through preheat zone 10 by any suitable method, including e.g.
radiant heat, direction injection of superheated steam, direct
combustion, and so on. Often, it may be convenient for preheater 11
to comprise a heat exchange unit that transfers thermal energy from
a preheating fluid (e.g., steam, combustion gases, etc.), into the
fluid to be heated. Fluid that exits preheat zone 10 is referred to
herein as preheated fluid and may be subjected to an additional
heating step referred to as a trim heating step and described in
detail later herein. Preheater 11 may preheat the fluid to a
nominal temperature but some variation (e.g., in the range of plus
or minus 1, 3, 7, or more degrees C.) may exist in the temperature
of the preheated fluid. Such variations in the temperature of the
preheated fluid may occur in particular over the lateral extent of
the below-discussed expansion zone (and so in some cases may thus
be caused primarily by flow behavior in the expansion zone, as
discussed later herein, rather than by any nonuniformity in the
heating accomplished by preheater 11). Such temperature variations,
regardless of their cause, may be compensated for (that is, the
fluid temperature may be finely controlled) by the trim heaters
disclosed later herein.
[0016] Apparatus 1 further comprises an expansion zone 20 that is
fluidly connected to preheat zone 10 in order to receive preheated
fluid therefrom. The exemplary expansion zone 20 depicted in FIGS.
1, 2 and 3 comprises first major wall 21, second major wall 22, and
first and second minor walls 23 and 24. Expansion zone 20 comprises
a downstream axis as described above and at any point along the
downstream axis will comprise a lateral extent measurable along a
lateral axis, and a tertiary extent measurable along a tertiary
axis.
[0017] Expansion zone 20 comprises inlet 25 through which preheated
fluid is received from preheat zone 10. Inlet 25 comprises a
lateral extent and a tertiary extent and a cross sectional area.
Expansion zone 20 comprises outlet 26 through which preheated fluid
exits expansion zone 20. Outlet 26 comprises a lateral extent and a
tertiary extent and a cross sectional area. As can be seen in FIG.
1 and in particular in FIG. 3 (which presents a front view of
expansion zone 20), significant lateral expansion may occur in
progressing downstream from inlet 25 to outlet 26. In various
embodiments, expansion zone 20 comprises a lateral expansion factor
(defined as the lateral extent of expansion zone 20 at outlet 26,
divided by the lateral extent of expansion zone 20 at inlet 25) of
at least about 2.5, at least about 3.5, or at least about 4.5. This
lateral expansion can be further characterized in terms of lateral
expansion angle .alpha. (as shown in FIG. 3), which is the angle at
which a minor side wall of expansion zone 20 deviates from the
downstream axis of expansion zone 20. In various embodiments,
lateral expansion angle .alpha. is at least about 15, at least
about 20, or at least about 24 degrees. It may often be convenient
for the lateral expansion to be symmetric (as in FIGS. 1 and 3),
but other arrangements are possible.
[0018] As can be seen in FIG. 1 and in particular in FIG. 2 (in
which expansion zone 20 is visible in side view), significant
tertiary contraction may occur in progressing downstream from inlet
25 to outlet 26. In various embodiments, expansion zone 20
comprises a tertiary contraction factor (defined as the tertiary
extent of expansion zone 20 at inlet 25, divided by the tertiary
extent of expansion zone 20 at outlet 26) of at least about 4.0, at
least about 5.0, or at least about 6.0. This tertiary contraction
can be further characterized in terms of tertiary contraction angle
.beta. (as shown in FIG. 2), which is the angle at which a major
wall (e.g., wall 22 of FIG. 2) of expansion zone 20 deviates from
the downstream axis of expansion zone 20. In various embodiments,
tertiary contraction angle .beta. is at least about 4.0, at least
about 6.0, or at least about 8.0 degrees. It will be recognized
that the characterization in terms of angle .beta. is applicable to
the particular exemplary embodiment of FIG. 2, which is an
asymmetric design in which one major side wall (wall 21) of
expansion zone 20 is generally aligned with the downstream axis
while the other (wall 22) deviates from the downstream axis to
provide the tertiary contraction. It is also possible to have both
side walls deviate from the downstream axis, in which case the
contraction can be characterized in terms of an angle exhibited by
each major side wall. In such case, in various embodiments such
angles can be at least about 2.0, at least about 3.0, or at least
about 4.0 degrees.
[0019] The above-described significant lateral expansion combined
with the significant tertiary contraction provide outlet 26 of
expansion zone 20 with a high aspect ratio, meaning the ratio of
the lateral extent of outlet 26 to the tertiary extent of outlet
26. In various embodiments, the aspect ratio of outlet 26 of
expansion zone 20 may be at least about 25:1, at least about 35:1,
or at least about 45:1.
[0020] In various exemplary embodiments, expansion zone 20 may
comprise a lateral extent at inlet 25 of at most about 80 inches
(203 cm), at most about 50 inches (127 cm), or at most about 31
inches (79 cm). In further exemplary embodiments, expansion zone 20
may comprise a lateral extent at outlet 26 of at least about 90
inches (229 cm), at least about 120 inches (305 cm), or at least
about 140 inches (356 cm). In various exemplary embodiments,
expansion zone 20 may comprise a tertiary extent at inlet 25 of at
least about 10 inches (25 cm), at least about 15 inches (38 cm), or
at least about 19 inches (48 cm). In further embodiments, expansion
zone 20 may comprise a tertiary extent at outlet 26 of at most
about 6.0 inches (15 cm), at most about 5.0 inches (13 cm), at most
about 4.0 inches (10 cm), or at most about 3.0 inches (7.6 cm). In
various exemplary embodiments, the cross sectional area of inlet 25
may be greater than that of outlet 26, by a factor of at least
about 1.1, at least about 1.2, or at least about 1.3. It will be
appreciated that the above numerical values are merely exemplary
illustrations, and that the particular design of apparatus 1 may be
varied as desired. For example, the angle of lateral expansion
and/or tertiary contraction may not be constant (that is, major
walls 21 and/or 22; and/or minor walls 23 and/or 24, may be arcuate
rather than generally planar as illustrated in FIG. 1). It will
also be appreciated that, while the term "expansion zone" has been
used for convenience in describing this zone, this terminology
merely signifies that this zone exhibits at least some increase in
lateral extent along the downstream direction of the zone. As
mentioned above, a decrease in tertiary extent may occur in the
downstream direction of the zone, such that the cross sectional
area of the zone outlet may be smaller than that of the zone inlet.
Thus, the characterizing of this zone as an expansion zone refers
merely to lateral expansion; it does not imply that any overall
expansion of the cross sectional area in the downstream direction
must necessarily occur, and it does not imply that expansion of
(e.g., reduction in density of) the fluid as it flows downstream in
the zone must necessarily occur.
[0021] Apparatus 1 further comprises an expanded zone 30 that is
fluidly connected to expansion zone 20 in order to receive
preheated fluid therefrom. The exemplary expanded zone 30 depicted
in FIGS. 1 and 2 comprises first major wall 31, second major wall
32, and first and second minor walls 33 and 34. Expansion zone 20
comprises a downstream axis as described above and at any point
along the downstream axis will comprise a lateral extent measurable
along a lateral axis, and a tertiary extent measurable along a
tertiary axis.
[0022] Expanded zone 30 comprises inlet 35 through which preheated
fluid is received from expansion zone 20. Inlet 35 comprises a
lateral extent and a tertiary extent and a cross sectional area. In
some embodiments, the lateral and tertiary extent of inlet 35 of
expanded zone 30 are substantially equal to (e.g., are not more
than 5% different from) those of outlet 26 of expansion zone 20. In
some embodiments, the lateral and tertiary extents of expanded zone
30 may be substantially constant (e.g., do not vary by more than
5%) along the downstream axis of expanded zone 30. In other
embodiments, either the lateral or tertiary extent of expanded zone
30 may change along the downstream axis of expanded zone 30 (for
example, downstream outlet 60 of expanded zone 30 may be narrower
in either tertiary or lateral extent, in comparison to inlet
35).
[0023] The aspect ratio (lateral extent to tertiary extent) of
expanded zone 30 may be at least about 25:1, at least about 35:1,
or at least about 45:1. The aspect ratio may be substantially
constant downstream through expanded zone 30. Or, it may vary
somewhat, in which case separate aspect ratios may be defined at
inlet 35 and outlet 60, either of which may comprise an aspect
ratio of at least about 25:1, at least about 35:1, or at least
about 45:1. While expanded zone 30 (and inlet 35 and outlet 60
thereof, and also outlet 26 of expansion zone 20) may be
characterized as having a high aspect ratio this does not
necessarily imply a strictly rectangular configuration (e.g., with
strictly straight major and minor walls). That is, generally oval
or elliptical designs are within the scope of the disclosures
herein.
[0024] Expanded zone 30 may comprise a first elbow 37 and/or a
second elbow 38. It will be understood that the provision of such
elbows, and other aspects of the design of apparatus 1, may be in
response to specific spatial and geometric constraints present in
the installation of apparatus 1 in a particular environment. More,
or fewer, elbows, bends, etc. can be used, the downstream extent
(length) of expanded zone may be varied, etc., as may be suitable
for a particular circumstance. Often, the lateral and tertiary
extents of expanded zone 30 may remain generally constant through
such elbows, but this may not be necessary in all cases.
[0025] Expanded zone 30 comprises a plurality of (e.g., at least
two) secondary heaters 40 that are used for fine control of the
temperature of the fluid and are referred to for convenience herein
as trim heaters. Trim heaters 40 can serve to augment preheater 11,
e.g. to provide a more precisely controlled temperature of the
fluid, particularly across the lateral axis of expanded zone 30.
Preheated fluid after having been exposed to (e.g., by passing in
contact with or in close proximity to) a trim heater 40 will be
referred to for convenience as trim-heated fluid (regardless of
whether or not a particular trim heater of the plurality of trim
heaters is actually delivering heat at the particular moment that a
particular parcel of preheated fluid is exposed to the trim heater,
as is discussed in further detail later herein).
[0026] Trim heaters 40 are individually controllable; i.e., each
trim heater 40 can be supplied with power, and/or brought to a
particular temperature, independently of other trim heaters 40.
Trim heaters 40 collectively extend across at least a portion of
the lateral extent of expanded zone 30. While in some circumstances
it may be desired to provide trim heaters 40 along only a portion
of the lateral extent of expanded zone 30, in some circumstances it
may be desired that trim heaters 40 collectively extend across the
entire lateral extent of expanded zone 30. It may be convenient to
provide the plurality of trim heaters 40 aligned generally linearly
at a particular location along the downstream axis of expanded zone
30 (as in the exemplary embodiment of FIG. 4) although it is also
possible that they could be staggered along the downstream axis of
expanded zone 30.
[0027] Trim heaters 40 may comprise any suitable heater which may
heat the fluid by any suitable method, including those discussed
above with regard to preheater 11. In some embodiments, it may be
advantageous that trim heaters 40 function by direct heating (e.g.,
by the passing of an electric current through the heater) rather
than by using a heat exchange fluid. In some embodiments it may be
advantageous that trim heaters 40 are low-pressure drop heaters
(e.g., that may protrude into the fluid flowstream within expanded
zone 30, but that present a relatively small resistance to gaseous
fluid flow). A particularly convenient type of trim heater is a low
pressure drop, electric heater comprising a rod comprised of a
resistive conductor within a metal sheath. In specific embodiments,
the rod may be formed into a cylindrical open coil of the general
design shown in FIGS. 4 and 5, although other geometric designs are
possible. Such electrical resistance heaters may be obtained e.g.
from Watlow Co., Hannibal, Mo., under the trade designation WATROD
Tubular Heaters. Such trim heaters may be operated in an on/off
mode (in which they can either be turned off, or activated at a
constant power). However, it may be preferable that trim heaters 40
be variably controllable, to enhance the fine control of the
temperature of the trim-heated fluid.
[0028] Trim heaters 40 may be spaced across the lateral extent of
expanded zone 30 e.g. with the long axis of each trim heater 40
aligned generally with the lateral axis of expanded zone 30. (In
this context, the term spaced does not imply that there is
significant lateral space between each trim heater and/or between
minor walls 32 and 34 and the trim heater closest to that wall;
rather, the trim heaters may be arranged so that such spaces are
minimal, e.g. less than 0.5 inch [1.3 cm]). For example, a suitable
number of cylindrical open-coil trim heaters may be provided in
parallel (i.e., aligned end-to-end along their long axes) across
the lateral extent of expanded zone 30 at a particular point along
the downstream axis of expanded zone 30. Two trim heaters 40, the
rightmost being the closest trim heater to wall 34 of expanded zone
30, are shown in such a configuration in FIG. 5. For optimum
performance, it may be helpful to position each trim heater
approximately centered along the tertiary axis of expanded zone 30
(i.e., approximately centered between major walls 31 and 32, as
shown in FIGS. 4 and 5). In some embodiments, one or more
additional trim heaters may be placed in downstream series with an
upstream trim heater (that is, placed downstream of the upstream
trim heater and at least partially aligned with it along the
lateral axis of expanded zone 30).
[0029] While the plurality of trim heaters 40 are described above
in the exemplary embodiment of trim heaters that are physically
separate units (e.g., as shown in exemplary manner in FIG. 5), in
the context used herein, a plurality of trim heaters also
encompasses a single physical unit that comprises at least two
individually controllable sections (i.e., sections which can be
supplied with power, and brought to a particular temperature,
independently of each other) along the lateral extent of the single
physical unit. That is, it is not required that the at least two
individually controllable sections are not physically connected to
each other.
[0030] Expanded zone 30 further comprises at least one fluid
flow-distribution sheet 50 that extends across at least a portion
of the lateral extent of expanded zone 30. In some embodiments, the
at least one fluid flow-distribution sheet 50 extends substantially
across the lateral extent and substantially across the tertiary
extent of expanded zone 30, e.g. so that at least 90% of the fluid
passing through expanded zone 30 passes through openings of the
fluid flow-distribution sheet 50. (Fluid flow-distribution sheet 50
may comprise a single continuous sheet, may comprise several pieces
abutted together to collectively provide fluid flow-distribution
sheet 50, etc).
[0031] Fluid flow-distribution sheet 50 may redistribute the flow
of preheated fluid, and/or trim-heated fluid, so as to provide a
more uniform distribution of flow velocity and/or temperature,
particularly across the lateral extent of expanded zone 30.
Specifically, fluid flow-distribution sheet 50 may compensate for
flow and/or temperature non-uniformities that may occur due to the
large lateral expansion factor of expansion zone 20 (since such a
large lateral expansion factor may cause boundary layer separation,
vortex shedding, generation of large scale eddies, and the
like).
[0032] Fluid flow-distribution sheet 50 may be placed at any
desired location along the downstream axis of expanded zone 30.
While it might be expected that best performance might be obtained
by providing a fluid flow-distribution sheet 50 upstream from trim
heaters 40 (e.g., so that a more uniform flow velocity and
temperature distribution might be obtained upstream of the trim
heaters, so that the trim heaters can more easily achieve the
desired fine control of the fluid temperature), it has surprisingly
been found that placing fluid flow-distribution sheet 50 downstream
of trim heaters 40 can provide substantial benefits. That is, trim
heaters 40 which may be provided upstream of any fluid
flow-distribution sheet 50 (e.g., at a location in which
large-scale flow and/or temperature non-uniformities might be
expected to be present) may provide sufficient fine control of
temperature that, in concert with a downstream fluid
flow-distribution sheet 50, the advantageous results disclosed
herein may be obtained.
[0033] Fluid flow-distribution sheet 50 may comprise any sheet
material that comprises suitable openings that permit flow of
gaseous fluid therethrough. Such a sheet material may be chosen
from e.g. mesh screens (whether of a regular pattern such as a
woven screen, or of irregular pattern such as an expanded-metal or
sintered metal mesh). Such a sheet material may also be chosen from
perforated sheeting, e.g. perforated metal sheeting. Fluid
flow-distribution sheet 50 may be distinguished from flow-alignment
elements (e.g., such as honeycombs with the long axes of the flow
channels oriented in the direction of flow of the fluid) that may
not provide the desired redistribution or mixing of the fluid
flow.
[0034] In some embodiments, the fluid flow-distribution sheet 50
may be a low-pressure-drop fluid flow-distribution sheet, defined
herein as a fluid flow-distribution sheet with a percent open area
of at least about 25% and an average opening size of at least 0.06
inch (1.5 mm). Such parameters may be measured straightforwardly
e.g. for perforated sheeting (with the average opening size being
the diameter in the case of generally circular openings, or the
equivalent diameter in the case of noncircular openings). It has
surprisingly been found that such a low-pressure-drop fluid
flow-distribution sheet may achieve satisfactory uniformity of the
fluid flow and/or temperature across the lateral extent of expanded
zone 30, with minimal pressure drop. In various embodiments,
low-pressure-drop fluid flow-distribution sheet 50 may comprise a
perforated sheet in which the average opening size is at least
about 0.08 inch (2.0 mm), at least about 0.10 inch (2.5 mm), or at
least about 0.12 inch (3.0 mm). In further embodiments, the average
opening size may be at most about 0.4 inches (10 mm), at most about
0.3 inches (7.6 mm), or at most about 0.2 inches (5.1 mm). In
various embodiments, the percent open area may be at least about
30%, at least about 35%, or at least about 40%. In further
embodiments, the percent open area may be at most about 75%, at
most about 60%, at most about 50%, or at most about 45%.
[0035] Fluid flow-distribution sheet 50 may be placed generally
normal to the direction of overall fluid flow (e.g., as shown in
FIG. 4). If desired, fluid flow-distribution sheet 50 may be angled
somewhat across the lateral and/or tertiary extent of expanded zone
30. In some embodiments, more than one fluid flow-distribution
sheet 50, e.g. low-pressure-drop fluid flow-distribution sheet 50,
may be provided in downstream series (i.e., one after the other, in
spaced relation downstream) in expanded zone 30. For example, the
exemplary embodiment of FIG. 4 depicts first fluid
flow-distribution sheet 50, second fluid flow-distribution sheet
51, and third fluid flow-distribution sheet 52, in downstream
series. It has been found that the use of multiple fluid
flow-distribution sheets 50 in this manner may provide enhanced
uniformity of fluid flow and/or temperature across the lateral
extent of expanded zone 30.
[0036] In some embodiments, series-downstream fluid
flow-distribution sheets 50 may be spaced apart along the
downstream axis of expanded zone 30 by a distance that is at least
as large as the tertiary extent of expanded zone 30 (that is, the
distance between walls 31 and 32). In some embodiments, the
farthest-downstream fluid flow-distribution sheet (sheet 52 in the
case of FIG. 4) may be recessed upstream from outlet 60 a distance
that is at least as large as the tertiary extent of expanded zone
30. Since the fluid flow immediately downstream of a fluid
flow-distribution sheet 50 may comprise jets emitting from the
perforations, interspersed with stagnant regions adjacent the solid
portions of the sheet, it may be advantageous to recess the
farthest-downstream fluid flow-distribution sheet in this manner to
ensure that the fluid flow is sufficiently uniform by the time the
fluid reaches outlet 60.
[0037] Outlet 60 is provided at a terminal end of expanded zone 30,
as shown in exemplary manner in FIG. 4. Trim-heated fluid can be
delivered through outlet 60 for any suitable purpose (for example,
to be impinged on and/or passed through a substrate as discussed in
detail later herein). For convenience of description, working face
61 of outlet 60 is defined as the plane through which trim-heated
fluid exits outlet 60 and that is bounded by components (e.g.,
terminal ends of walls) of outlet 60. For optimum control of flow
velocity and/or temperature of the trim-heated fluid, the lateral
and tertiary extent of working face 61 of outlet 60 may be
generally similar to (e.g., within 5% of), or substantially
identical to, the lateral and tertiary extent of expanded zone 30.
Working face 61 of outlet 60 may be characterized in terms of an
aspect ratio (the ratio of the lateral extent of working face 61 to
the tertiary extent of working face 61). In various embodiments,
working face 61 may comprise an aspect ratio of at least 25:1,
35:1, or 45:1.
[0038] In some embodiments, expanded zone 30 may comprise elbow 38
that is proximate outlet 60, as shown in the exemplary embodiment
of FIG. 4. As mentioned previously, the presence or absence of one
or more elbows in apparatus 1 may be chosen, or dictated, by the
particular spatial and geometric constraints of the equipment
(e.g., substrate forming or processing equipment) with which
apparatus 1 is to be used. If an elbow 38 is used that is proximate
outlet 60, in some embodiments a generally straight section of
expanded zone 30 may be provided between elbow 38 and working face
61 of outlet 60 that is at least as long as the tertiary extent of
expanded zone 30. In some embodiments, elbow 38 will comprise a
radius of curvature that is at least as large as the tertiary
extent of expanded zone 30.
[0039] In some embodiments, a plurality of temperature sensors 62
may be provided in expanded zone 30, proximate outlet 60 and spaced
across the lateral extent of expanded zone 30. Temperature sensors
62 may detect any variations in the temperature of the trim-heated
fluid across the lateral extent of expanded zone 30 and thus may
allow trim heaters 40 to be individually controlled so as to
achieve the herein-disclosed fine control of the temperature of the
trim-heated fluid, across the lateral extent of expanded zone 30.
Thus, in this manner, trim-heated fluid may be delivered from
outlet 60 that has a very uniform temperature profile across the
lateral extent of working face 61 of outlet 60.
(Alternatively, the power delivered to each trim heater may be
controlled so that the temperature profile varies over the lateral
extent of the outlet, if this is desired.) In some embodiments, the
plurality of temperature sensors 62 are provided with each
temperature sensor being generally downstream from (i.e., generally
laterally aligned with) a particular trim heater 40, so that the
temperature reading from a particular temperature sensor can be
used to control the operation of a particular trim heater 40. The
temperature reported by the various temperature sensors can be
monitored by an operator who can adjust the power supplied to the
individual trim heaters accordingly. However, it may often be
convenient that the data provided by the temperature sensors be
supplied to a process control mechanism that automatically controls
the power inputted to the trim heaters based on the data provided
by the temperature sensors.
[0040] Temperature sensors 62 may all be the same, or some may
differ from each other. In some embodiments, temperature sensors 62
may each be a thermocouple, e.g. an open junction thermocouple. In
various embodiments, J-type thermocouples or E-type thermocouples
may be conveniently used. The temperature-sensitive portion (e.g.,
tip end) of each temperature sensor 62 may be placed so that it
protrudes into the stream of trim-heated fluid, without causing
unacceptable pressure drop. It has been found advantageous to
position temperature sensors 62 slightly upstream from working face
61 (e.g., a distance that is at least 30% of the tertiary extent of
expanded zone 30), as shown in FIG. 4. In particular embodiments in
which elbow 38 is present, it has been found advantageous to
position the temperature-sensitive tip of temperature sensors 62
somewhat toward the major surface of expanded zone 30 that is a
continuation of the radially-outermost surface of expanded zone 30
at elbow 38 (thus, for example, in the exemplary embodiment of FIG.
4, the tip of temperature sensor 62 is displaced somewhat toward
major wall 31).
[0041] Outlet 60 may comprise flanges 63 and 64 that flank working
face 61 on both tertiary sides and that may extend substantially
along the entire lateral extent of working face 61. Such flanges
may advantageously provide mechanical strength and stability to
outlet 61, so as to minimize vibration and the like. In various
embodiments, flange 63 and 64 may be about 1/2 to 2 inches in width
(along the tertiary axis of working face 61 of outlet 60). When
used to deliver heated fluid onto a substrate, outlet 60 may be
positioned so that working face 61 is any convenient distance from
the substrate, e.g. from about 0.5 inch (1.3 cm) to about 5 inches
(12.7 cm). In particular embodiments, working face 61 may be from
about 1.0 inch (2.5 cm) to about 2.0 inches (5.1 cm) from the
substrate.
[0042] The walls (e.g., major and minor walls) that at least partly
define the various zones (preheat zone 10, expansion zone 20,
expanded zone 30) of apparatus 1 may be made e.g. of sheet metal,
such as sheet steel, as is common practice. The various zones may
be conveniently provided as separate sections that are then
attached together, e.g. with the assistance of
externally-protruding flanges as are visible in FIG. 1. However,
such sectional assembly and/or externally-protruding flanges are
not required (and are omitted in FIGS. 2 and 3. If desired, thermal
insulation 39 (e.g., a fibrous blanket or the like) may be provided
in any or all of preheat zone 10, expansion zone 20, and/or
expanded zone 30. It may be particularly advantageous to provide
such insulation in at least a portion of expanded zone 30 (e.g., as
shown in exemplary manner in FIGS. 1 and 2) so as to maintain a
finely-controlled fluid temperature achieved by the methods
disclosed herein. Such insulation may extend downstream all the way
to outlet 60 if desired. At whatever downstream point of a zone
that insulation 39 is provided, it may surround the zone (for
example, over a particular downstream extent of expanded zone 30,
insulation 39 may be provided that is outwardly adjacent, and
optionally in contact with, walls 31, 32, 33 and 34). If desired,
expanded zone 30 may comprise a hinge 68 located at any suitable
position so that outlet 60 may be more easily maneuvered and
positioned (e.g., a laterally-oriented hinge which allows outlet 60
to be moved toward and/or away from a substrate). In some
embodiments, apparatus 1 may not comprise any flow-altering element
of any type (whether the particular fluid flow-distribution sheet
50 as described herein, or any other type of fluid
flow-distribution or flow control element) in expansion zone 20. In
some embodiments, apparatus 1 may not comprise any flow modifier or
turbulence-inducing apparatus in between working face 61 of outlet
60 and a substrate upon which the heated fluid is impinged. In some
embodiments, expanded zone 30 may not comprise any flow-alignment
members (i.e., vanes or dividers oriented generally downstream and
serving to divide the expanded zone into lateral sections). The
heated (e.g., pre-heated and trim-heated) fluid can be any gaseous
fluid, with air often being most convenient to use.
[0043] As has already been noted, the design of apparatus 1 can be
varied as needed for a particular purpose and/or to fit a
particular environment. For example, the dimensions, angles, etc.,
of the various zones can be selected as needed. Furthermore,
apparatus 1 need not be limited to the specific number of zones as
disclosed above. For example, expanded zone 30 might in some cases
be followed (downstream) by another expansion zone (e.g. a
secondary expansion zone), which itself might be followed by
another expanded zone (e.g., a secondary expanded zone), which may
or may not contain trim heaters and/or fluid flow-distribution
sheets.
[0044] Those of ordinary skill will appreciate that apparatus 1 and
methods of using have been discussed above with reference to an
exemplary configuration (e.g., as shown in FIGS. 1-3) in which
preheat zone 10, expansion zone 20, and expanded zone 30, have
discrete and unambiguously identifiable boundaries therebetween.
However, it will be appreciated that this may not necessarily be
the case in every design. For example, preheat zone 10 might
comprise a configuration in which the lateral extent of preheat
zone 10 increases along the downstream axis of at least a portion
of preheat zone 10 (e.g., a portion proximate to expansion zone
20), such that it may not possible to state with certainty exactly
where preheat zone 10 ends and expansion zone 20 begins. That is,
the designation of where inlet 25 of expansion zone 20 is located
along the downstream axis of preheat zone 10 and expansion zone 20,
may be somewhat arbitrary. Likewise, expanded zone 30 might
comprise a configuration in which the lateral extent of expanded
zone 30 increases along the downstream axis of at least a portion
of expanded zone 30 (e.g. a portion proximate to expansion zone
20), such that it may not be not possible to state with certainty
exactly where expansion zone 20 ends and expanded zone 30 begins.
That is, the designation of where outlet 26 of expansion zone 20,
and inlet 35 of expanded zone 30, are located along the downstream
axis of expansion zone 20 and expanded zone 30, may be somewhat
arbitrary. All such possible variations are included within the
scope of the disclosures herein. For example, one such variation
might comprise an apparatus in which the lateral extent of the
apparatus continuously expands along the downstream axis of the
apparatus, with the exact locations of the boundaries between the
preheat zone, the expansion zone, and the expanded zone thus being
somewhat arbitrary.
[0045] Apparatus 1 as described herein may be used for any
application in which it is desired to deliver trim-heated fluid,
e.g. onto a substrate. In some embodiments, the substrate may be a
moving substrate 70, as pictured in exemplary manner in FIG. 6. In
particular embodiments, moving substrate 70 may be a fibrous web
made of fibers that are bonded together at least to a certain
extent (e.g., melt-blown fibers). In other embodiments, moving
substrate 70 may be a fibrous mat comprising fibers that are not
bonded together (e.g., organic polymeric melt-spun fibers, as made
e.g. in a process such as described in U.S. Patent Application
Publication 2008/0038976 to Berrigan et. al., incorporated herein
by reference). In such cases, apparatus 1 may be used to pass
trim-heated fluid through the fibrous mat in order to promote
bonding (e.g., melt-bonding) of at least some of the fibers to each
other (such a process will be referred to herein as through-air
bonding). Apparatus 1 may advantageously allow such through-air
bonding to be performed in a uniform manner even on very wide
moving substrates (e.g., fibrous mats of over about 70 inches [178
cm], 90 inches [229 cm], or 110 inches [279 cm] in width, and even
up to approximately 132 inches [335 cm] in width or more).
Apparatus 1 may be particularly useful when the fibrous mat is a
monocomponent mat comprised of monocomponent organic polymeric
fibers (e.g., polypropylene). In such monocomponent mats, there may
be a much narrower window of temperatures over which through-air
bonding can be successfully performed than for fibrous mats
comprising e.g. multicomponent (e.g., bicomponent) fibers. That is,
bicomponent fibers often comprise a portion (e.g., a core) of a
relatively high melting material, and a portion (e.g., a sheath) of
a relatively low melting material. Thus, there may be a relatively
wide temperature range in which the sheath portion is meltable so
as to bond the fibers to each other, while the core portion remains
unmelted and provides mechanical stability. In contrast,
monocomponent fibers may have a narrow temperature window for
through-air bonding, below which no bonding may occur, and above
which unacceptably high deterioration of fiber properties may
occur. Thus, the fine temperature control enabled by the apparatus
and methods disclosed herein may be particularly suitable for the
through-air bonding of monocomponent fibrous mats. In the
particular application of through-air bonding of monocomponent
polypropylene fibers, it may be desired to deliver trim-heated
fluid at a temperature in the general range of 130-155 degrees
C.
[0046] In various embodiments, preheater 11 of preheat zone 10 may
be used to preheat fluid to a nominal temperature that is slightly
lower than the target temperature of the trim-heated fluid, with
trim heaters 40 used as necessary to bring the fluid to the final
(target) temperature. In various embodiments, one or more trim
heaters may additionally heat the preheated fluid by a temperature
increment of no more than about 15 degrees C., of no more than
about 7 degrees C., of no more than about 3 degrees C., or of no
more than about 1 degrees C. Since the preheated air may exhibit
variations in temperature, at any given time during the operation
of apparatus 1 different trim heaters 40 may be operated at
different power levels and thus may be heating the preheated fluid
by different temperature increments. In certain instances (e.g.,
particularly when apparatus 1 has run for sufficiently long time to
achieve generally steady-state operation), one or more of trim
heaters 40 may only need to be used sporadically, or possibly not
at all. Thus, use of the apparatus and methods disclosed herein may
not necessarily require every trim heater 40 to be powered
(delivering heat) at all times.
[0047] Trim-heated air may be delivered through working face 61 of
outlet 60 at a linear velocity of, e.g., between about 400 feet
(122 meters) per minute and about 3000 feet (912 meters) per
minute. Particularly when used for purposes of through-air bonding
of a fibrous mat, it may be advantageous to provide suction on the
opposite side of the moving substrate (fibrous mat), in order to
capture and remove the trim-heated fluid after it has passed
through the moving substrate. This may be performed by the use of
suction apparatus 80 as shown in exemplary manner in FIG. 6. Moving
substrate 70 may be carried e.g. on a porous belt 81 (e.g., mesh or
the like) with suction apparatus 80 placed underneath. Suction
apparatus 80 may comprise a lateral extent that is at least as wide
as the lateral width of moving substrate 70 and that may be similar
to, equal to, or greater than, the lateral extent of working face
61 of outlet 60. Suction apparatus 80 may be designed to capture
and remove a portion (e.g., at least about 80 volume %), or
generally all, of the trim-heated fluid that is passed through
moving substrate 70. In some embodiments, suction apparatus may be
operated to capture and remove more fluid than is delivered through
outlet 61, in which case some portion of ambient air may be drawn
through moving substrate 70 and removed by suction apparatus
80.
[0048] If apparatus 1 is to be used in combination with a
melt-spinning apparatus, other suction apparatus or zones may also
be used. For example, a first suction apparatus may be used to aid
in the collection of the spun fibers as a fibrous mat, which is
then conveyed to a second suction apparatus which performs to
remove trim-heated air passed through the mat in the course of
through-air bonding, as described herein. If desired, one or more
additional suction apparatus may be used as desired to provide heat
treatment, quenching, etc., of the through-air bonded spun-bonded
fibrous web. All of these suction apparatus may be different
apparatus (e.g., operated at different conditions); alternatively,
two or more of the suction apparatus may be zones of a single
suction apparatus of sufficient extent (e.g., down the direction of
movement of moving substrate 70) to perform the multiple functions.
The fluid that is collected and removed by any or all of such
suction apparatus may be recirculated to the inlet of preheat zone
10 (e.g., by the afore-mentioned blower fan), if desired.
[0049] While being described herein primarily in the context of
providing trim-heated fluid that may be very uniform across the
lateral extent of the outlet as it exits the outlet of the
apparatus (and, e.g., as it is impinged onto a substrate), the
apparatus and methods disclosed herein allow very precise
temperature control that may be used to other ends. For example, it
may be possible to vary the temperature of the trim-heated air
across the lateral extent of the outlet, e.g. in order to produce
substrates with downweb-oriented stripes that have received
different thermal exposures. In addition, in some instances it may
be helpful to adjust the operation of the trim heaters (e.g., the
power delivered thereto) based on observation of the properties of
the heated substrate (e.g. the lateral variation of certain
properties of the substrate), rather than solely relying on the
temperature readings provided by the temperature sensors.
Furthermore, while the operation of apparatus 1 has been described
above primarily with regard to its use for delivering heated fluid
for purposes of bonding a fibrous mat (substrate), many other uses
are possible, and may be applied to any suitable substrate,
article, or entity, moving or unmoving. For example, apparatus 1
may be used for delivering heated fluid for purposes of drying,
annealing or any other type of heat treatment, promoting a chemical
reaction, etc.
LIST OF EXEMPLARY EMBODIMENTS
Embodiment 1
[0050] An apparatus for handling, heating and delivering a fluid,
comprising:
[0051] a preheat zone comprising a preheater; an expansion zone
fluidly connected to the preheat zone; an expanded zone fluidly
connected to the expansion zone and comprising a downstream axis
and a lateral extent and a tertiary extent, the expanded zone
further comprising: a plurality of trim heaters collectively
extending across at least a portion of the lateral extent of the
expanded zone, at least one fluid flow-distribution sheet, and, an
outlet.
Embodiment 2
[0052] The apparatus of embodiment 1 wherein the plurality of trim
heaters collectively extend across the lateral extent of the
expanded zone.
Embodiment 3
[0053] The apparatus of any of embodiments 1-2 wherein the trim
heaters comprise electrical resistance heaters.
Embodiment 4
[0054] The apparatus of any of embodiments 1-3 wherein the
preheater comprises a heat exchanger configured to heat the fluid
by exchanging thermal energy to the fluid from a preheating
fluid.
Embodiment 5
[0055] The apparatus any of embodiments 1-4 wherein the at least
one fluid flow-distribution sheet is positioned downstream of the
plurality of trim heaters.
Embodiment 6
[0056] The apparatus any of embodiments 1-5 wherein the fluid
flow-distribution sheet comprises a perforated sheet with the
perforations providing a percent open area of from about 30% to
about 70% and having an average size of from about 0.06 inch (1.5
mm) to about 0.40 inch (10 mm).
Embodiment 7
[0057] The apparatus of any of embodiments 1-6 comprising at least
two fluid flow-distribution sheets arranged in series along the
downstream axis of the expanded zone.
Embodiment 8
[0058] The apparatus of any of embodiments 1-7 comprising at least
three fluid flow-distribution sheets arranged in series along the
downstream axis of the expanded zone.
Embodiment 9
[0059] The apparatus of embodiment 8 wherein the at least three
fluid flow-distribution sheets are spaced apart along the
downstream axis of the expanded zone by distances equal to or
greater than the tertiary extent of the expanded zone.
Embodiment 10
[0060] The apparatus of any of embodiments 1-9 wherein the outlet
is spaced downstream from the fluid flow-distribution sheet that is
closest to the outlet, by a distance that is greater than the
tertiary extent of the expanded zone.
Embodiment 11
[0061] The apparatus of any of embodiments 1-10 wherein the outlet
comprises a working face and wherein the expanded zone comprises a
plurality of temperature sensors spaced across the lateral extent
of the expanded zone and positioned a distance upstream from the
working face of the outlet that is greater than about 30% of the
tertiary extent of the expanded zone, with a temperature-sensitive
tip of each temperature sensor protruding into the fluid.
Embodiment 12
[0062] The apparatus of any of embodiments 1-11 wherein the
expansion zone comprises a lateral expansion factor of at least 3.5
and a tertiary contraction factor of at least 4.0.
Embodiment 13
[0063] The apparatus of any of embodiments 1-12 wherein the
expansion zone comprises a lateral expansion factor of at least 5.0
and a tertiary contraction factor of at least 5.0.
Embodiment 14
[0064] The apparatus of any of embodiments 1-13 wherein the
expansion zone comprises a lateral expansion angle of at least 15
degrees.
Embodiment 15
[0065] The apparatus of any of embodiments 1-14 wherein at least
the expanded zone comprises thermal insulation that surrounds at
least a portion of the expanded zone.
Embodiment 16
[0066] The apparatus of any of embodiments 1-15 wherein the outlet
comprises a working face with an aspect ratio of at least 35:1.
Embodiment 17
[0067] The apparatus of any of embodiments 1-16 wherein the
apparatus further comprises a fluid-suction apparatus configured to
be placed on the on the opposite side of a fluid-permeable, moving
substrate from the outlet, wherein the fluid-suction apparatus has
a lateral width at least as wide as the lateral width of the
substrate.
Embodiment 18
[0068] The apparatus of any of embodiments 1-17 wherein the
expanded zone comprises a laterally-oriented hinge.
Embodiment 19
[0069] A method of passing a heated fluid through a moving,
fluid-permeable substrate, comprising: preheating a fluid; passing
the preheated fluid through an expansion zone; passing the
preheated fluid through an expanded zone, exposing at least a
portion of the preheated fluid to at least one of a plurality of
trim heaters within the expanded zone, passing at least a portion
of the preheated fluid through at least one fluid flow-distribution
sheet within the expanded zone; and, passing the preheated fluid
through an outlet of the expanded zone onto the moving,
fluid-permeable substrate and passing it through the substrate;
and, capturing and removing at least a portion of the fluid passed
through the substrate, by a fluid-suction apparatus located on the
opposite side of the substrate from the outlet.
Embodiment 20
[0070] The method of embodiment 19 wherein the moving,
fluid-permeable substrate is a monocomponent melt-spun fibrous mat
comprising monocomponent organic polymeric fibers.
Embodiment 21
[0071] The method of any of embodiments 19-20 wherein the expanded
zone comprises a plurality of temperature sensors downstream from
the trim heaters, and wherein the fluid temperature readings
monitored by the temperature sensors are used to control the power
supplied to the trim heaters.
Embodiment 22
[0072] The method of any of embodiments 19-21 wherein the trim
heaters collectively extend across a lateral extent of the expanded
zone, wherein the temperature sensors are spaced across the lateral
extent of the expanded zone, and wherein the power supplied to each
trim heater is controlled based on the fluid temperature reported
by a temperature sensor that is generally downstream of, and
laterally aligned with, that trim heater.
Embodiment 23
[0073] The method of any of embodiments 19-22 wherein the trim
heaters additionally heat the preheated fluid by a temperature
increment of less than about 3 degrees C.
Embodiment 24
[0074] The method of any of embodiments 19 to 23, wherein the
method uses an apparatus comprising any of embodiments 1-18.
Embodiment 25
[0075] A method of delivering a heated fluid, comprising:
preheating a fluid; passing the preheated fluid through an
expansion zone; passing the preheated fluid through an expanded
zone, exposing at least a portion of the preheated fluid to at
least one of a plurality of trim heaters within the expanded zone,
passing at least a portion of the preheated fluid through at least
one fluid flow-distribution sheet within the expanded zone; and,
delivering the preheated fluid through an outlet of the expanded
zone.
Embodiment 26
[0076] The method of embodiment 25, wherein the method uses an
apparatus comprising any of embodiments 1-18.
Example
[0077] A heated-air delivery apparatus was constructed of the
general design shown in FIGS. 1-6. The apparatus comprised a
preheat zone with a lateral extent of 30 inches and tertiary extent
of 20 inches (as defined by sheet steel walls), and comprised a
three-stage, steam-supplied heat exchanger preheater. The preheat
zone contained an inlet that was fed with ambient air motivated by
a conventional blower fan.
[0078] The outlet of the preheat zone was fluidly connected to the
inlet of an expansion zone, with the inlet having a lateral extent
of 30 inches (76 cm) and a tertiary extent of 20 inches (51 cm) and
being aligned with the outlet of the preheat zone. Major and minor
walls of the expansion zone were configured so that, over a
downstream distance of approximately 125 inches (318 cm), the
lateral extent expanded to about 146 inches (371 cm) and the
tertiary extent contracted to about 3 inches (7.6 cm), as measured
at the outlet of the expansion zone. This corresponded to a lateral
expansion factor of approximately 4.9 and a lateral expansion angle
of about 25 degrees, and to a tertiary contraction factor of
approximately 6.7 and a tertiary contraction angle of about 8
degrees (all as defined previously herein).
[0079] The outlet of the expansion zone was fluidly coupled to an
inlet of an expanded zone, which inlet was of the same lateral and
tertiary dimensions as (and aligned with) the outlet of the
expansion zone. The expanded zone comprised a downstream straight
run of a few inches, followed by an elbow, followed by a straight
run of approximately twelve feet (3.6 meter), followed by another
elbow, followed by a straight run of a few inches, terminating in a
flanged outlet, in similar manner as depicted in FIGS. 1 and 2. The
major and minor walls were substantially parallel to each other
over the entire downstream length of the expanded zone, so that the
cross sectional area of the expanded zone did not change over the
downstream length of the zone, and so that the outlet
(specifically, the working face thereof) comprised a lateral extent
of approximately 146 inches (371 cm) and a tertiary extent of
approximately 3 inches (7.6 cm).
[0080] Trim heaters were provided at a point approximately 11 feet
(3.3 meter) downstream from the first elbow of the expanded zone.
The trim heaters each comprised an electrical-resistance heater
made from a rod of diameter approximately 0.32 inches (0.8 cm),
formed into a cylindrical open coil of diameter approximately 2.5
inches (6.4 cm) at a coil-spacing of approximately 1.6 coils per
inch (2.5 cm), and were custom-fabricated by Watlow Co., Hannibal,
Mo. The long axes of all of the cylindrical coils were co-aligned
with the lateral axis of the expanded zone. Nine such heaters with
a length of approximately 14 inches (36 cm) were used, collectively
laterally flanked by two similar heaters (one on each lateral side)
each about 8 inches (20 cm) in length. In this manner the trim
heaters collectively extended over the entire approximately 146
inch (371 cm) lateral extent of the expanded zone. Each trim heater
was centered within the approximately 3.0 inch (7.6 cm) tertiary
extent of the expanded zone. Each trim heater comprised electrical
connections so that it could be independently powered and
controlled.
[0081] Three fluid flow-distribution perforated sheets were
provided. The first was positioned approximately 5.9 inches (15 cm)
downstream from the trim heaters (as measured from the downstream
surface of the trim heaters), with the next two positioned at
intervals of approximately 4.0 inches (10 cm) downstream of the
preceding fluid flow-distribution sheet. All of the perforated
sheets extended over essentially the entire tertiary and lateral
extent of the expanded zone and were positioned generally normal to
the air flow. Each perforated sheet comprised 14 gauge aluminum
with approximately 0.125 inch (3.2 mm) diameter round holes, on
approximately 0.1885 inch (4.8 mm) center to center spacings in a
60 degree hexagonal array (approximately 24.1 holes per square inch
[6.5 square cm]), providing a percent open area of approximately
40.3.
[0082] The second elbow was positioned approximately 14.6 inches
(37 cm) downstream from the trim heater (as measured from the
downstream surface of the trim heaters to the upstream end of the
elbow). The elbow comprised a radius of curvature of approximately
4.4 inches (11 cm). A straight run of approximately 3 inches (7.6
cm) was present from the downstream end of the elbow, to the
outlet. The outlet comprised a working face that was flanked on
each tertiary side by flanges that each extended approximately 1.0
inches (2.5 cm) along the tertiary axis of the outlet, and that
extended along the entire lateral extent of the outlet. The flanges
were comprised of metal and had a thickness (along the downstream
axis of the outlet) of approximately 0.5 inches (1.3 cm).
[0083] J-type open-junction thermocouples were attached to the
radially innermost major surface of the straight-run that extended
between the second elbow and the outlet (in similar manner as shown
in FIG. 4, except that each thermocouple was mounted to the
radially inner major surface instead of the radially outer major
surface as shown in FIG. 4). Each thermocouple was positioned so
that its temperature-sensitive tip end was located about 2.2 inches
(5.6 cm) upstream from the working face of the outlet, and was
located approximately 1 inch (2.5 cm) inward from the radially
outermost surface (thus approximately 2 inches (5.1 cm) outward
from the radially innermost surface). A plurality of thermocouples
were provided, spaced along the lateral extent of the expanded
zone, so as to provide measurement of the temperature of the air
across the lateral extent of the expanded zone (at a point slightly
upstream from the outlet, as stated above). The placement of the
thermocouples and the spacing intervals therebetween (approximately
14 inches [36 cm] for most) was chosen so that each thermocouple
was laterally aligned with (that is, aligned approximately near the
lateral center of) one of the above-described trim heaters.
[0084] The apparatus was operated in conjunction with a melt
fiber-spinning apparatus which was used to form a mat of
monocomponent polypropylene fibers. The fiber-spinning apparatus
(of the general type described in U.S. Patent Application
Publication 2008/0038976 to Berrigan et. al.) was used to
continuously deposit a fibrous mat of approximately 132 inches (335
cm) in lateral extent, onto a moving mesh carrier that was used to
carry the fibrous mat underneath (with respect to conventional
gravitational orientation) the above-described outlet with the long
axis of the fibrous mat oriented perpendicular to the lateral axis
of the outlet. A suction apparatus was provided underneath the
carrier and was aligned with the above-described outlet, was
similar in lateral extent to the outlet, and was approximately 6
inches (15 cm) in extent along the tertiary axis of the outlet
(which axis was aligned with the direction of motion of the carrier
and fibrous mat). In various cases the fibrous mat was carried
underneath the outlet at speeds ranging from 90 to 130 feet (229 to
330 cm) per minute, which (in combination with the three-inch [7.6
cm] tertiary extent of the working face of the outlet) resulted in
a residence time of the fibrous mat in the trim-heated air exiting
the outlet of from approximately 0.1-0.2 seconds.
[0085] In various experiments, air was supplied to the apparatus by
the above-described blower fan. The above-described preheater was
fed with steam at, e.g., approximately 200 psi (14 bar),
corresponding to a temperature in the range of 190-200 degrees C.
This resulted in preheating the air to a nominal temperature that
was often in the range of, e.g., 130-145 degrees C. In various
experiments, typical linear velocities of trim-heated air emerging
from the outlet were in the range of approximately 600 to about
2400 feet (182 to 730 meters) per minute. In many instances, a
suction ratio of approximately 1:1 was used (that is, the suction
apparatus removed generally all of the spent trim-heated air, but
did not remove a substantial amount of ambient air as well). In
other cases a slightly higher suction ratio (e.g., in the range of
1.1-1.5) was used. The above-described thermocouples were used to
monitor the temperature of the trim-heated air as it approached the
outlet, and the trim heaters were controlled by a process control
system operating in view of the temperatures reported by the
thermocouples. In various experiments, it was found that use of the
preheater in combination with the trim heaters could provide
trim-heated air that varied over time (at particular locations
along the lateral extent of the outlet) by less than approximately
plus or minus 0.5 degrees C., and in some cases by less than
approximately plus or minus 0.1 degree. In various experiments
(e.g., with the temperature of the trim-heated air being in the
range of approximately 130-150 degrees C.), it was found that the
entire lateral extent of fibrous webs comprising monocomponent
polypropylene fibers could be generally uniformly through-air
bonded using the apparatus and methods described above.
[0086] The tests and test results described above are intended
solely to be illustrative, rather than predictive, and variations
in the testing procedure can be expected to yield different
results. All quantitative values in the Examples section are
understood to be approximate in view of the commonly known
tolerances involved in the procedures used. The foregoing detailed
description and examples have been given for clarity of
understanding only. No unnecessary limitations are to be understood
therefrom.
[0087] It will be apparent to those skilled in the art that the
specific exemplary structures, features, details, configurations,
etc., that are disclosed herein can be modified and/or combined in
numerous embodiments. All such variations and combinations are
contemplated by the inventor as being within the bounds of the
conceived invention. Thus, the scope of the present invention
should not be limited to the specific illustrative structures
described herein, but rather extends at least to the structures
described by the language of the claims, and the equivalents of
those structures. To the extent that there is a conflict or
discrepancy between this specification and the disclosure in any
document incorporated by reference herein, this specification will
control.
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